If you're thinking about buying a new or used green car, you're not alone. High gas prices look like they're here to stay, so more car shoppers than ever before are considering hybrid, diesel and electric vehicles.

Still, some wonder about the downside. Is hybrid/electric technology fully proven yet? Could expensive components fail and put a dent in your wallet? Are most hybrids unpleasant to drive? And could the new "clean diesel" vehicles really be that clean?

These are good questions to ask, but the upside of green cars generally outweighs the downside. A new or used example can be an excellent choice -- just heed our tips and shop wisely.

Shopping for a Gas-Electric Hybrid Car

A gas-electric hybrid car uses a conventional gasoline motor in tandem with an electric motor that's hooked to a battery pack. The idea is that the electric motor takes a lot of the stress off the gasoline motor, resulting in superior fuel economy -- especially in urban driving.

There are two basic kinds of gas-electric hybrids that you should be aware of. The most popular kind, which we'll call the conventional hybrid, uses the electric motor primarily as a supplement, so it can't really drive on electric power alone -- at least not for any great distance. One example is the Toyota Prius. The other kind, known as the plug-in hybrid, can drive solely on electric power until the battery pack runs out of juice. At that point, the gas engine takes over, but even then the gas engine and electric motor still work together. In fact, the Chevrolet Volt uses the gasoline engine to make electricity. A car like the Honda Accord Plug-in Hybrid reverts to a more conventional hybrid set-up once the batteries are depleted. To keep driving on electricity only, you have to plug in the car for some time.

If you're shopping for a gas-electric hybrid, there are a few important tips to keep in mind.

First, there's no way around the higher price of new hybrids relative to similar non-hybrid vehicles. It typically takes years to earn back those extra dollars with what you're saving on gasoline. As such, we recommend taking a close look at used hybrids, since depreciation can definitely help close the price gap.

Second, with regard to used hybrids, don't worry too much about reliability issues -- at least not with more recent hybrid models. Hybrid components generally have long warranties that should transfer to used-hybrid buyers. When these long warranties expire, however, all bets are off. Older Honda Civic hybrids, for example, have developed a reputation for burning out battery packs at $2,000 to $4,000 a pop. Therefore, we strongly advise looking for a used hybrid with significant time remaining on the hybrid-component warranty.

Third, the driving character of hybrids varies widely from model to model. The original Prius, for example, may have given hybrids a bad name with its grabby brakes and strange engine noises, but newer hybrids are much better. Examples include the Ford Fusion Hybrid, the Toyota Highlander Hybrid, Volkswagen Jetta Hybrid and the eAssist mild hybrids from General Motors (e.g., the Chevrolet Malibu, Chevrolet Impala and Buick Regal). We recommend driving as many hybrids as you can to get an idea of what they're like on the road.

Finally, think hard about plug-in pros and cons before signing on the dotted line. Cars like the Volt are so pricey that they're more like lifestyle accessories than practical modes of transportation. The technology is awesome, no doubt, but just remember that it doesn't come cheap. Cars like the Chevrolet Volt and Nissan Leaf are more affordable when you check the lease deals. You should be able to lease a Nissan Leaf for about $200 per month.

Shopping for a Diesel-Powered Car

If hybrids seem like a bridge too far, we suggest diesel vehicles as a more down-to-earth alternative. Diesel fuel, if you're wondering, is a less-refined kind of fuel that's sort of like heating oil. In other words, it's no more exotic than the stuff that keeps snow-belt residents warm in the winter. Also, diesel engines generally last longer than gasoline engines.

Diesel-powered cars and trucks are more fuel efficient than their gas-powered counterparts. That's why they're part of the green car conversation. In fact, cars like the Volkswagen Passat TDI can be even more fuel efficient on the highway than popular hybrids like the Camry.

Compared to hybrids, however, diesels get worse fuel economy in the city, so that's something to keep in mind if urban driving is a big part of your routine.

Another concern that many people have about diesels is air pollution. Indeed, diesels used to be known for excessive particulate emissions, which are particularly harmful to the environment. However, because of very strict U.S. government regulations, most of the new clean diesel engines minimize these harmful emissions via advanced systems that inject a cleansing agent into the vehicle's exhaust stream. Accordingly, we now recommend diesels to the environmentally inclined without reservation. If they meet U.S. regulations, yes, they're really that clean.

Another point in favor of diesel-powered vehicles is their excellent drivability. Diesel engines have superior torque, for one thing, which means you get a nice shove off the line when you punch the accelerator -- just the way we Americans like it. But more than that, diesel vehicles are otherwise like any other car, so the steering, brakes and all the rest will be just like what you're accustomed to in your current ride. That's why we say diesel vehicles are a great way to "go green" without giving up proper driving dynamics.

One caution, though: self-serve diesel pumps in the U.S. often aren't as well-maintained as gas pumps, because their primary users are no-nonsense, big-rig truckers. So watch out for greasy handles and that sort of thing. Also, not all filling stations even sell diesel, so you may have to plan ahead a little more -- especially on longer trips.

Shopping for an Electric Car

Despite all the press they've received, pure electric cars still account for less than 1 percent of all vehicles on the road, and that's unlikely to change much for the foreseeable future. So if you decide to go electric, you're definitely taking the road less traveled.

That's not necessarily a bad thing, though. Electric cars such as the Nissan Leaf and Tesla Model S have a lot to offer, including quiet, smooth "instant-on" power that can make fossil-fueled vehicles feel clunky by comparison. Also, electric cars have fewer moving parts, which should translate to lower maintenance costs over the long haul.

But there are good reasons electric cars don't have more of a presence on our roads. First, their limited driving range effectively takes long road trips out of the equation. Even though charging stations are starting to appear along heavily traveled highway routes, you'll still have to wait a long time for that depleted battery pack to recharge.

Then there's the issue of price. If you thought hybrids were expensive, wait until you price electric cars. To be fair, the Nissan Leaf has become more affordable as of late, but it should still run you at least $30,000, and you're basically getting economy-car style and character for that price. As for the aforementioned Tesla, it's a beautiful car inside and out, but even the base model is likely to set you back more than the cost of two Leafs. Yes, there are tax credits to sweeten the deal, but you'll still end up paying a lot for any electric car.

Our advice to electric-car shoppers, therefore, is simple: Bring money, and unless you never have to drive long distances, make sure you've got access to another car. But if you can cover both those bases, hey, there's no doubt that electric cars are really cool.

When shopping for any environmentally friendly car, first examine your needs. If you have a long commute, a pure electric car might not work for you. Those with an even mix of highway and city driving or those who commute long distances will probably be happiest with a diesel-powered car. Hybrids are sort of the catch-all for people who want to use less fuel and don't mind paying a little extra to buy the car in the first place. Finally, consider a used car if saving money is among your main goals in owning an environmentally friendly car.

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